The technology explosion in the implantable medical device (IMD) industry has resulted in many new and innovative devices and methods for analyzing the health of a patient and/or providing therapies to improve quality of life. IMDs include pacemakers, implantable cardioverter-defibrillators (ICDs), neural stimulators, drug administering devices, monitors, etc. State-of-the-art IMDs are capable of performing significantly more complex tasks and are vastly more sophisticated and complex than earlier IMDs and their therapeutic benefits have been well established.
There are many IMDs that provide data acquisition of important physiologic data from a human body, e.g. cardiac IMDs that acquire cardiac data. Such cardiac IMDs include implantable heart monitors that only monitor and acquire cardiac data and therapy delivery IMDs that both acquire cardiac data and provide appropriate therapies, such as single chamber, dual chamber, and bi-ventricular pacemakers, ICDs that typically incorporate pacing systems for treating bradycardia and tachyarrhythmias, and cardiomyostimulators. The therapy delivery cardiac IMDs comprise an implantable pulse generator (IPG) that is coupled with one or more electrical medical lead bearing electrodes for sensing the inter-cardiac or remote electrogram (EGM) and/or delivering pacing pulses or cardioversion/defibrillation shocks to the heart.
Cardiac IMDs and other IMDs can include the capability of communicating, through radio frequency telemetry transmissions, with external medical devices to enable programming and interrogation of the IMD through downlink telemetry transmissions and to enable uplink telemetry transmissions of data from the IMD to the external medical device.
Cardiac IPGs and monitors as well as other IMDs are powered by an internal power source, typically one or more batteries, that serves a variety of functions, including, but not limited to, supplying power to electronic components and circuitry and charging high voltage capacitors that are discharged through medical electrical leads into the heart to regulate heart rhythms. The functional sophistication and complexity of the IMD operating systems powered by the battery have increased over the years. Battery powered IMDs must be replaced when the battery become depleted, and therefore conserving battery power is important to maintain or prolong the life of the IMD. Therefore, much effort has been devoted to increasing conservation of battery resources.
The IMD electronics include a microcontroller that is operated in accordance with stored software, or firmware, or a combination of both. Generally, the microcontroller is programmed to respond to events as they are detected by other discrete components of the IMD electronics. With each response to the events, the depletion of the battery is increased. What is needed are power conservation techniques that optimize the operation of the microcontroller as a function of responding to the events.